*5.1.1. Dolphin pox*

132 New Approaches to the Study of Marine Mammals

them more susceptible to viral infections.

indicators of environmental stress.

A study conducted during 2006 and 2007 revealed notable differences in skin diseases between two communities of Guiana dolphins (*Sotalia guianensis*) from Brazil [43].The authors found that the community, living in the chemically and biologically polluted Paranaguá estuary, was characterized by the occurrence of lobomycosis-like and nodular skin diseases. This estuary is known for its high levels of chlorinated hydrocarbons, as well as regular oil spills. In contrast, another community of Guiana dolphins, living in the less polluted Cananéia estuary, was free from these skin diseases and had relatively low tissue levels of organochlorines. The authors consequently proposed that lobomycosis-like and

A southern right whale neonate that beached along the Southern coast of South Africa and suffering from extensive skin lesions were found to be infected with a number of cutaneous fungi including *Chaetomium globosum, Chaetomium murorum* and *Penicillium coprophilum* [44]. During the same period, another southern right whale neonate was found beached and suffering from a yeast infection caused by *Candida zeylanoides* [45]. In both cases the authors

Maldini and co-workers [46] reported on bottlenose dolphins living in Monterey Bay, California. Their research, conducted between 2006 and 2008, showed that approximately 90% of these cetaceans were characterized by skin lesions. They identified five skin conditions, with pox-like lesions being the most frequently found. The authors suspected that contaminants such as persistent organic pollutants (POPs) and heavy metals were contributing factors that weakened the immune systems of the dolphins, thereby rendering

A recent study on North Pacific humpback whales (*Megaptera novaeangliae*) examined bacterial species associated with the skin of these mammals [47]. It was found that healthy individuals were characterized by similar microbial communities, as opposed to healthcompromised individuals that harboured different populations. Also, the microbial populations on the skin of these animals were found to be different to that of the seawater, which led to the conclusion that the skin-associated bacteria were adapted to live on the epithelium and its constituents. The study also reported that the bacterial phylum found most on healthy individuals is Bacteroidetes*,* in contrast to the health-compromised

Cetaceans are also exposed to UV radiation and often exhibit lesions similar to skin cancer in humans [48]. Interestingly, cetacean species with darker pigmentation have less UVR induced skin damage. Also, latitude affects the incidence of this phenomenon, since UVR

A recent study by Fury and Reif [49] reported poxvirus lesions in two estuarine populations of bottlenose dolphins from Australia. This was the first report of poxvirus-like lesions in Australian cetaceans. Their results suggested that these infections were accompanied by climatic events, such as flooding in this case, which lead to lower water salinity and higher occurrence of dolphin pox. They concluded that diseases such as dolphin pox, might act as

individuals which harboured Gammaproteobacteria as the dominant group.

dosage at lower latitudes, are 5 times higher than at mid-latitudes.

speculated about anthropogenic factors contributing to the condition of the animals.

nodular skin diseases might act as indicators of environmental burden.

*Poxviridae* represent the largest family of viruses known to cause diseases in marine and terrestrial mammals [50]. Among cetaceans, the odontocetes seem to be more affected than the mysticetes [49]. Species of cetaceans reported to be affected by pox viruses, include Atlantic bottlenose dolphins [7, 50], bottlenose dolphins from Australia [49], Atlantic whitesided dolphins [7, 50], common dolphin (*Delphinus delphis*), dusky dolphins, white-beaked dolphins (*Lagenorhynchus albirostris*) [29, 50], striped dolphins (*Stenella coeruleoalba*) [29, 50], Hector's dolphins (*Cephalorhynchus hectori*) [7, 29, 50], long finned pilot whales (*Globocephala melaena*) [29, 50], as well as a few spp. of porpoises [50].

Dolphin pox has been associated with a variety of lesions, referred to as 'targets', wateredsilk', 'ring', 'pinhole', 'circle' and 'tattoo'-like [7]. These lesions emerge as single or overlapping circular grey spots. Later, these ring lesions may develop into black punctiform stippled patterns. Histological studies revealed a thickened stratum corneum with ballooning degeneration, and eosinophilic inclusions containing virus particles, inside the cytoplasm of stratum intermedium cells. Studies on this disease pointed to one consistent feature; its relationship with compromised environmental conditions and consequent general health of affected individuals [7, 51].

## *5.1.2. Herpes virus*

Herpes virus had been reported as the causative agent of focal dermatitis in captive, as well as free-swimming beluga whales [51, 52]. Lesions caused by this virus appeared as multiple grey, raised, pale grey regions on the skin, which eventually ulcerated and healed very slowly. At the time of infection, these whales appeared to be in poor health and under stress. Histological analyses showed epithelial cells that underwent intercellular oedema, necrosis and the development of microvescicles. Prominent eosinophilic, intra-nuclear, inclusion bodies were evident in infected epithelial cells [51].

### *5.1.3. Papillomavirus in cetaceans*

In cetaceans, papillomas have been reported on the skin, as well as the tongue, penis, pharynx and first gastric compartment [51].
